There is a long-standing need for leg braces for knees impaired by temporary or permanent loss of neuromuscular control or by loss of control of a knee joint through a knee injury. For stability or bracing, such knee braces must have stays or brace members secured firmly to the leg both below and above the knee with a knee joint housing between the brace members.
It is generally realized, as is discussed in the Lewis et al. U.S. Pat. No. 4,361,142, that it is particularly difficult to provide orthopedic knee appliances which provide stability while still duplicating or accommodating the complex flexion and extension actions which a knee undergoes. At the same time the braced knee joint must effectively duplicate the compound, complex, actions of a normal knee. Otherwise the knee brace may well be injurious to the user.
A study of the prior art shows that duplication of normal knee actions has not been fully accomplished. Thus knee braces generally have been rigid in both the knee bending direction and in the knee straightening direction unless a manually operated release is incorporated in them. As one example a double-locking ratchet knee joint, pivotally connected between the upper and lower leg, is described in U.S. Pat. No. 4,520,804. Relative pivotal movement between the knee joint and upper and lower leg sections is achieved manually by a pair of actuatable locking levers. Rotary movement of the ratchet wheel is effected only by manual rotation of a locking pawl control lever. Presently, then, it is not possible to straighten the leg as in normal walking, especially for traveling up steps.
An object of this invention is to provide a knee brace allowing a leg bent at the knee to be straightened while at the same time being prevented from buckling in the knee bending direction.
Another object of the invention is the provision of a knee brace which is releasable so that it can free wheel in both directions when it is not in use, that is, under a no load condition.
Still another object is to provide a knee brace which will lock in any position because its locking mechanism functions in small increments.
Existing knee brace locking devices have been either cone clutches, roller type clutches or single pawl ratchet devices. Variations in friction due to clutch surface conditions, as well as the distance pawls must normally travel before engaging or locking, can lead to a knee joint which gives way. My issued patent, U.S. Pat. No. 5,490,831 overcame many of these disadvantages, but as noted in the prior art, there is still room for improvement. This invention embraces a major step in that direction.